In the fields of semiconductor devices, flat panel displays, and micro electro mechanical systems (MEMS), a structure (hereinafter referred to as a “microstructure”) having a micropattern formed on its surface is manufactured by the use of, for example, a lithography technique.
An optical inspection apparatus is used for the inspection of such a microstructure. The conventional inspection apparatus applies a light to an inspection target pattern formed on a substrate such as a wafer from, for example, a laser light source or a lamp light source, detects a reflected light from the pattern by a detector, and compares the signal intensity of the detected light by, for example, die-to-die comparison, thereby conducting a defect inspection.
Recently, patterns having high aspect ratios have been produced due to advanced miniaturization and integration of the microstructures. For example, in a trench pattern having a high aspect ratio, defects can be generated at various locations in a depth direction (see FIG. 4A).
However, there have heretofore been a problem of defect detection failures resulting from a small amount of information only obtained by the signal intensity of the detected light, and a problem of the decrease of the S/N ratio of a defect dependent on the height (depth) of the defect.